At a Glance

Why Get Tested?

When to Get Tested?

When you have joint pain and fatigue that your health care provider suspects may be due to RA

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Rheumatoid factor (RF) is an autoantibody, an immunoglobulin M (IgM) protein that is produced by the body's immune system. Autoantibodies attack a person's own tissues, mistakenly identifying the tissue as "foreign." While the biologic role of RF is not well understood, its presence is useful as an indicator of inflammatory and autoimmune activity. This test detects and measures RF in the blood.

Is any test preparation needed to ensure the quality of the sample?

The Test

How is it used?

The rheumatoid factor (RF) test is primarily used to help diagnose rheumatoid arthritis (RA) and to help distinguish RA from other forms of arthritis or other conditions that cause similar symptoms.

While diagnosis of RA relies heavily on the clinical picture, some of the signs and symptoms may not be present or follow a typical pattern, especially early in the disease. Furthermore, the signs and symptoms may not always be clearly identifiable since people with RA may also have other connective tissue disorders or conditions, such as Raynaud phenomenon, scleroderma, autoimmune thyroid disorders, and systemic lupus erythematosis, and display symptoms of these disorders as well. The RF test is one tool among others that can be used to help make a diagnosis when RA is suspected.

When is it ordered?

The test for RF may be ordered when a person has signs and symptoms of RA. Symptoms may include pain, warmth, swelling, and morning stiffness in the joints, nodules under the skin, and, if the disease has progressed, evidence on X-rays of swollen joint capsules and loss of cartilage and bone. An RF test may be repeated when the first test is negative and symptoms persist.

A cyclic citrullinated peptide (CCP) antibody test can help diagnose RA in someone who has joint inflammation with symptoms that suggest but do not yet meet the criteria of RA and may be ordered along with RF or if the RF result is negative.

What does the test result mean?

The RF test must be interpreted in conjunction with a person's symptoms and clinical history.

In those with symptoms and clinical signs of rheumatoid arthritis, the presence of significant concentrations of RF indicates that it is likely that they have RA. Higher levels of RF generally correlate with more severe disease and a poorer prognosis.

A negative RF test does not rule out RA. About 20% of people with RA will have very low levels of or no detectable RF. In these cases, a CCP antibody test may be positive and used to confirm RA.

Is there anything else I should know?

The 2010 Rheumatoid Arthritis Classification Criteria from the American College of Rheumatology (ACR) includes cyclic citrullinated peptide (CCP) antibody testing, along with RF, as part of its criteria for diagnosing rheumatoid arthritis. According to the ACR, CCP antibodies may be detected in about 50-60% of people with early RA, as early as 3-6 months after the beginning of symptoms. Early detection and diagnosis of RA allows health practitioners to begin aggressive treatment of the condition, minimizing the associated complications and tissue damage.

2. Can an RF test be performed in my doctor's office?

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Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Rindfleisch, J. A. and Muller, D. (2005 September 15). Diagnosis and Management of Rheumatoid Arthritis. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20050915/1037.html through http://www.aafp.org.

(Revised 2009 April). Handout on Health: Rheumatoid Arthritis, National Institute of Arthritis and Musculoskeletal and Skin Diseases [On-line information]. Available online at http://www.niams.nih.gov/Health_Info/Rheumatic_Disease/default.asp through http://www.niams.nih.gov. Accessed March 2009.

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This article was last reviewed on March 31, 2014. | This article was last modified on June 1, 2014.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.